Growth Responses of Alaska Pea Seedlings to Visible Radiation and Gibberellic Acid.

Abstract

The time-course of stem growth of Pisum sativum, variety Alaska in response to visible irradiation and gibberellic acid has been measured. Under relatively low intensity red or blue light (0.1 to 100 ergs . cm-2 sec.-1) the growth of Alaska pea seedlings is markedly inhibited for 24 to 36 hours. Following this inhibition the plants resume a maximum rate of stem elongation (equal to dark-grown plants) in spite of continued irradiation. At higher radiation intensities (>100 ergs cm-2. sec.-1) the plants show the same inhibition and recovery but subsequent growth is somewhat less than the maximum (dark-grown) rate, and is a function of the light intensity. Gibberellic acid reverses both the low intensity and high intensity light inhibition of stem elongation. The low energy red: far-red pigment system does not appear to affect stem elongation in this plant.